GB827408A - Improvements in or relating to compressed-gas electric circuit interrupters - Google Patents

Abstract

827,408. Gas-blast switches; contact members for switches. WESTINGHOUSE ELECTRIC CORPORATION. May 31, 1957 [.Tune 7, 1956], No. 17338/57. Class 38 (5). A gas-blast switch has a tank 2 containing gas under pressure and enclosing interrupting assemblies 34 each comprising a main current interrupting unit 44 and a parallel-connected impedance interrupting unit 45. When a conducting cross-bar 36 is lowered, it initially opens a dump valve (not shown) in each assembly to connect a space 122 below a piston 82 through conduits 175, 184, exhaust chamber 58 and hollow bushing 27 to atmosphere. The piston 82 is moved down by the pressure within the tank to open the main contacts 90, 91 and the annular blast valve surrounding them. The resulting gas blast blows the arc through the nozzle contact 91 on to fixed and movable arcing contacts 64, 93 where the arc is extinguished, the current through the switch then flowing through the parallel contacts 67, 126 and resistor 54. Near the end of the opening stroke of the main contact 90, an extension of the arcing contact 93 strikes a valve stem 113 to open a second dump valve 116 which through conduits indicated at 127 interconnects the space 123 below the piston contact 126 with the space 122 so venting the space 123 to atmosphere. The piston is moved down to open the contacts 67, 126 and the annular blast valve surrounding them. The resulting arc is blown out by a blast of gas from the tank to interrupt the residual current through the resistor 54. The conducting cross-bar 36 now separates from disconnecting fingers 56 to interpose isolating gaps in series with the interrupting assemblies 34 and the first dump valve (not shown) recloses to permit pressure to build up in the spaces 122, 123 to reclose the contacts 90, 91 and 67, 127 and the second dump valve 116. The exhaust gases passing into the chamber 58 are also vented through the hollow bushing 27 which is provided with a spring-loaded outlet valve, Fig. 13 (not shown), to prevent complete loss of pressure in the tank 2. A three-phase switch may be formed by arranging three of the assemblies described on a common frame with the three cross-bars connected to a common pneumatic operating mechanism, Fig. 1 (not shown). Contact members for switches.-The main movable contact assembly comprises an annular contact 90 provided by resilient fingers 94 which co-operate with a vertical wall surface 91 of a stationary orifice contact 59. Fingers 88 engaging the side wall of the piston 82 maintain an electrical connection between the fingers 94 and piston 82 and the fixed conducting parts connected to the disconnecting contact 56. Fig. 20 shows a modified arrangement in which the upper surface of the piston forms the moving contact and the orifice contact has segmental finger contacts 256 pivoted at 261 and biased downwardly by springs 257. Semi-circular spacers 269 prevent the air-blast blowing the contacts 256 into the exhaust passage. Specification 687,051 and U.S.A. Specificaton 2,507,210 are referred to.